Friction draft-gear.



C. W. SHERMAN.

FRICTION DRAFT GEAR.

APPLICATION FILED APR. 23. 19m.

1 ,24 1 1 5 6 Patented Sept. 25, 1917.

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CLIFTON W. SHERMAN, OF BUFFALO, NEW YORK.

FRICTION DRAFT-GEAR.

Specification of Letters Patent.

Patented Sept. 25,1917.

Application filed April 23, 1914. Serial No. 833,898.

- To all whom it may concern:

Be it known that I CLIFTON W. SrIEnMAN, acitizen of the United States, residlng at Buffalo, in the county of Erie and State of New York, have invented new and useful Improvements in Friction Draft-Gears, of which the following is a specification.

This invention relates to, friction draft gears such as are used in railway cars for relieving the same from the shock, jar and strains while coupling and drawing the cars.

One of the objects of this invention is to providea draft gear of this character in which the frictional surfaces are more effective and the frictional engagement of the frictional elements is distributed more uniformly over these elements.

Another object of this invention is to 'so organize this friction draft gear that a prompt release of the friction elements is produced after the same have been subjected to bufiing or pulling strains and thereby enable the gear to relax promptly.

My invention has the further object to so organize the friction draft gear that the usual tie bolt which has heretofore been employed for holding the several parts of the friction gear in place may be dispensed with.

In the accompanying drawings:

Figure 1 is a horizontal longitudinal section of a friction draft gear'embodying one form of my improvements. Fig. 2 is a longitudinal sectional elevation of the same taken approximately in line 2'2, Fig. 1. Figs. 3, 4, 5 and 6 are vertical transverse sections taken in the correspondingly numbered lines in Fig. 1.

Similar characters of reference indicate corresponding'parts throughout the several views.

In its general organization this friction draft gear is like those heretofore in use and comprises side draft sills or beams 1, 1 which are arranged lengthwise and arallel in the lower part of the car body, ront and rear followers 2 and 3 which are guided between said sills so as to be capable of moving forward and backward horizontally, a pair of front stops or blocks 4 secured to the inner sides of the sills and operating to limit the forward movement of the front follower, a pair of rear stopsor blocks 5 arranged on the inner sides of the sills and operating to limit/the rearward movement of the rear follower, a car coupler. 6 provided with a draw bar or shank 7 arranged lengthwise in front of the front follower, and a yoke 8 connected with the draw bar and slidingly embracing the front and rear followers.

The organization of my improvements shown in Figs. 1-6, is constructed as follows:

9 represents an external friction member preferably constructed in the form of a cylinder which is oblong in cross section and which is arranged between the upper and lower straps of the yoke so that its major axis is horizontal and its minor axis vertical and bears with its closed rear or inner end.

sides with the bore of the friction cylinder adjacent to opposite ends of its major axis and each of which is rovided, with an inclined, beveled or we ge face 12 while its rear end is provided with a fiat transverse face 13.

Within this set of front shoes are arranged 1 a plurality of sections 14 of a wedge preferably two in number, as shown in Figs. 1, 3 and 4, these sections being arranged transversely side by side and in a direction parallel with the major axis of the friction cylinder. Each of the wedge sections is provided at its front or outer end with a fiat transverse face 16 bearing against the flat rear side of the front follower, an inclined or beveled intermediate face 17 adapted to bear against the inclined faces 12 of the adjacent front friction shoes, and a flat rear transverse face 19. The two sections of the front wedge are yieldingly held apart or pressed outwardly against the companion friction shoes by means which preferably comprise a transverse coil spring 20 arranged at its opposite ends in pockets or recesses 21 formed in theopposing sides of the front wedge sections, as shown in Figs.

1 and 4. The inner or rear set of friction elemen also comprises a' plurality of rear friction shoes 22 which bear against the bore of the friction cylinder'adjacent to opposite ends der.

of its major axis and each provided with an inclined or beveled face 23. Between the inner or rear friction shoes are arranged the sections 24: of inner or rear wedge, preferably two in number, which are arranged transversely side by side in a direction parallel with the major axis of the friction cylinder and each provided with an inclined or beveled face 25 engaging with the inclined faces on the adjacent shoes of the inner or rear set. The front ends of the rear sections are provided with fiat transverse faces 26 which bear against the flat inner or rear faces of thefront wedge sections so that longitudinal movement may be transmitted from one set of wedge. sections to the other but these wedge sections are free to move transversely toward or away from each other. The sections of the rear'wedge are held yieldingly against the companion rear friction shoes by means which preferably comprise a transverse spring 27 seated at its opposite ends in pockets or recesses 28 formed in the oppos. ing sides of the rear wedge sections.

29 represents a main. b'ufling or tension spring arranged within the inner or rear part of the friction cylinder and bearing at its rear end against the rear head of the cylinder while its front end bears against the rear ends of the rear set of friction shoes. At the rear ends of the rear wedge sections the same are provided with lateral extensions 30 which are constructed to form shoulders adapted to engage with the rear ends of the rear friction shoes and are also con-v structed to form a seat for the front end of a supplemental buffing or tension and releasing spring 32 which latter is arranged -within the main spring and bears at its rear end against the rear head of the cylin- Although the angle of the wedging engagement of the shoes and wedges may be varied, it is preferable to make the angle of the cooperating inclined faces of the rear or inner shoes and wedge sections more acute or sharp than the angle of the cooperating inclined faces of the front shoes and wedge sections, the angle of wedging engagement between the last mentioned parts being comparatively blunt or obtuse, as shown in Fig. 1.

In the normal position of the parts the faces 17 of the forward wedge are spaced from the inclined faces 12 of the blocks 11 and the bufling or tension springs 29, 32 are expanded as fully as the stops 4 and 5 will permit but are still under tension to take up slack and the front and rear followers bear respectively against the front and rear stops of the draft sills, as shown in Figs. 1 and 2. Upon pushing the coupler or draw bar backwardly or inwardly together with "the front follower in the act of coupling two cars, the movement of the front follower is transmitted to the front wedge sections and also to the rear wedge sections, which latter in turn bear against the front end of the supplemental tension spring 32, whereby the longitudinal movement of these parts in this direction is yieldingly resisted and cushioned. At the same time the rear wedge sections by the action of their inclined faces against those of the'rear set of friction shoes,

cause the latter to be pressed outwardly sections engage with the corresponding facesof the rear set of shoes;

This causes the rear wedge sections by their wedging engagement with the rear set of shoes to press the latter with increased frictional contact against the friction member and also cause the rear wedge sections to approach each other and compress the transverse spring 27 between the same. After initial part of the inward movement of the rear wedge sections independently of the rear shoes and while the rear wedge sections are still separated the inclined faces of the front wedge sections engage the corresponding faces of the front set of shoes and operate not only to press the latter transversely outward but also tend to slide the same inwardly along the bore of the friction cylinder. By reason of the spring and frictional resistance which opposes the inward movement of the outer or front set of shoes the latter can be pressed effectively by the bufiing or pulling blow both laterally against the friction cylinder and also inwardly against the rear set of shoes, thereby increasing the effectiveness of the cushioning device.

When the blow is only a moderate one the members of the front wedge sections 16 may be moved transversely inward toward each other by reason of their wedging engagement with the front shoes, whereby the spring 20 between these wedges is compressed to a greater extent and the frictional engagement of the front shoes with the cylinder is increased accordingly. lVhen,

however, the blow is veryheavy the front wedge sections are first caused to bear against each other by the wedge action of the. same against the front shoes so that during the remainder of the inward movement of the front wedge sections the same form practically a solid wedge and operate with greater effect both in pressing the front shoes laterally against the cylinder memes and also sliding the same inwardly lengthwise thereof. The inner wedge sections at no time act as a solid wedge inorder to avoid splitting the cylinder by reason of the powerful acute angle of the inclined faces of this wedge section. This action is best obtained by so determining the space between the inner wedge sections that they do not engage each other in their innermost longitudinal position into which the same are moved by the front wedge sections.

As the two sets of wedges are pushed rearwardly or inwardly, the tension upon the springs interposed between the respective members of these two sets of wedge sections is increased more or less in accordance with the strain to which they are subjected by the wedging action of these wedge sections against the friction shoes, thereby rendering the frictional action of both sets of friction shoes against the friction cylinand rear sets of friction shoes, whereby der more effective'and uniform. An added advantage in making the angle of the cooperating wedging surfaces of the inner or rear set of shoes and wedge sections more acute than the angle of the cooperating wedging surfaces of the outer or front set of shoes or wedge sections, as shown in Fig. 1, is that the frictional engagement of the front and rear set of friction shoes with the friction cylinder is by this means equalized or nearly so. This is due to the fact that the angle of engagement between the rear shoes and wedges causes these shoes to be moved outwardly and grip the friction cylinder firmly while their forward movement is resisted by the heavy spring 29 before the front shoesare pressed by their companion front wedge sections against the cylinder. It follows therefore from this that after the rear shoes engage with an increased. frictional contact with the cylinder the same ofier a more rigid abutment for the front shoes so that the latter offer a greater resistance to being moved inward lengthwise and can therefore be pressed with greater force by the slower acting .but greater blow resisting wedging surfaces of the front shoes and wedge sections. By this means a practically uniform pressure of increased efiiciency is gradually exerted against the friction cylinder by the front the strains are distributed over a greater area and the gear is rendered more durable, effective and less liable to be broken down under maximum strains.

During the initial part of the inward longitudinal movement of the wedge sections the movement of the friction shoes in the same direction is resistedby the longitudinally operating main spring 29 which latter is morepowerful than the'combined slrength of the longitudinally operating release. spring 32 engaging the inner ends of the inner wedge sections and the transversely operating springs 20, 27 between the sections, respectively, of the front and rear wedges. It follows from this that the main spring holds the friction shoes practically stationary so that they form an abutment agamst which the wedges can operate to press the shoes transversely outwardly and cause the latter to grip the cylinder with such frictional grip that the shoes offer the greatest possible resistance against a blow delivered against the same in a direction parallel with the frictional surface of the cylinder, thereby increasing the cushioning capacity of this draft gear during bufling and pulling action accordingly.

Inasmuch as the wedge sections are pushed inwardly first the inner or releasing spring 32 receives the primary or initial part of the bufiing strains. As the bufling strain. upon the coupler or draw bar is relaxed, both sets of wedges are simultaneously released by reason of the tension of the releasing spring 32 against the rear set of wedge sections which latter in turn transmit this releasing pressure against the front wedge sections, and the main tension spring 29 by its resilience pushes the rear set of shoes forwardly as well as the front set of shoes through the medium of the rear shoes. The wedges by this means are promptly released so that the pressure of the shoes against the friction cylinder may be relieved and not interfere with the quick relaxatiori of the gear.

This cushioning operation of the draft gear when two cars are being pulled or drawn apart while coupled is substantially the same as that which occurs while coupling two cars, inasmuch as while drawing the cars the front follower remains at rest against the front stops and the rear follower moves forwardly toward the front follower and causes the cylinder to move relatively to the friction shoes and wedges.

By constructing the friction cylinder of oblong form with its major axis arranged horizontally and transversely the extra width of cylinder is obtained to permit of introducing the wedge sections side by side between the members and each set of shoes and still keeping within the standard construction and arrangement of the draft sills and other main elements of cars now in common use.

The servicecondition to which a friction gear is subjected may be illustrated by one car traveling five miles an hour, and again the same car traveling ten miles per hour. We have a given weight with the inertia multiplied by doubling the speed. Again, we have for'illustration ten cars moving five milesper hour which may result in approximately the same inertia as one car running ten miles per hour. Ten cars moving ten inder o the draft miles per hour would givea combination of load and high speed of action on the draft gear. These four loads applied to any draft gear illustrates .the necessity of a device that will take care of light or heavy blows under fast or slow speeds and always furnishing the correct resistance or resiliency to properly cushion the cars.

It has been found that the angles of the shoes and wedge sections which give the correct resistance at a given speed of blow are not properly effective under faster or slower blows. Therefore the yielding wedge sections 24 having angles more nearly parallel to the line of travel tighten against the shoes 22 resistingly held by 'the heavy spring 29 causing more uniform frictional engagement with the cylinder 9' under varying speeds As the travel of the follower advances until the wedge sections 24 are nearly closed the shoes 11 are loosely carried forward in contact with inner shoes 22 and the blunt angle 12 and further travel of the shoes is resisted by the combination of the longitudinal springs and inner shoes. This total resistance is sufficient to retard the travel of the shoes 11--22 until the wedge sections 24 advance and further" increase the. outward pressure on the shoes 22 without bringing the wedge sections 24in con-- movement tending to a uniform frictional engagement under varying speed of blows. The frictionalresistance of each part is in-. creased in relation to the spring load at any point of the stroke.

It will be noted that in thls construction no separate means, such as tie bolts, are

to hold the shoes, wedges and cylears against longitudinal displacement re ttively to each other.

This friction draft gear involves no complication of parts, the same can be produced at comparatlvel low cost and effectively cushions heavy ufling and pulling strains.

' I claim as my invention:

1. A friction draft gear comprisin' a friction member, a plurality of sets of riction shoes and wedge sections arranged tandem, each of said sets comprising a plural-, ity of friction shoes bearing agamst the friction member and a plurality of wedge sections in wedging engagement with the companion shoes, a spring interposed between the wedge sectlons of each set, the inner ends of the wedge sections of the outer set bearing against the outer ends of the wedge sectlons of the inner set, and yieldshoes, a spring interposed between the wedge sections of each set, the'inner ends of the wedge sections of ,the outer set bearing against the outerends of the wedge sections of the inner set, and yielding means which resist the inward movement of said sets ofshoes and wedge sections comprising.a spring engaging with the inner ends of the shoes of the inner set, and a spring engaging'with the inner ends of the wedge sections of the inner set.

3. A friction draft gear comprising a friction member, a plurality of sets of friction shoes and wedge sections arranged tandem, each of said sets comprising a plurality of friction shoes bearing against the friction member and a plurality of wedge sections in wedging engagement with the companion shoes, a spring interposed between the wedge sections of each set, and yielding means which resist the inward movement of said sets of shoes and wedge sections, the angle of wedging engagement between the wedge sections and shoes nearer to said yielding means being more acute than the angle of wedging engagement between the wedge sections and shoes remoter from said yielding means.

4. A. friction draft gear. comprising a friction member, a set of outer friction shoes bearing against the friction member, a set of outer wedge sections engaging the outer shoes, a set of inner shoes bearing against the friction member, and a set of inner wedge sections engaging the inner shoes and the outer wedge sections and projecting laterally acros the inner ends of the outer shoes.

5. A friction draft gear comprising a friction member, a set of outer friction shoes bearing against the friction member, a set ofouter wedge sections engaging the outer shoes, a set of inner shoes bearing against the friction member, and a set of inner wedge sections engaging the inner shoes and also engaging the outer wedge sections.v

Witness my hand this 20th day of April, 1914.

- CLIFTON W. SHERMAN.

Witnesses: Tnno. L. Porr,

ANNA HEIGIS. 

